MOSCOW -- Anna Stepanova Trifonova, bundled in a green wool coat, trudged through the slush to the post office on Tsvetnoy Boulevard yesterday morning to try to keep her life's savings from being reformed out of existence.

She was No. 116 in line. A gray-haired, stooped crowd of pensioners milled in front of the post office, panicky and resentful. But after a while, a woman emerged and pinned a scribbled note to the door:

"For the Information of Pensioners. Today there will be no money exchange. For information, come tomorrow at 10."

"I have 1,000 rubles, in hundreds,for my funeral," said Mrs. Trifonova, 76, a stout woman who was a plasterer and janitor for 40 years.

She has three days to turn in her money before 50- and 100-ruble notes become worthless. In theory, she can get back 200 rubles, the no-questions-asked limit for pensioners, in smaller bills right away. She can get the other 800 rubles back only by proving that she acquired it legally.

Much of the money came from birthday and New Year's gifts from relatives over the years, she said.

"How can I prove that?" Mrs. Trifonova asked, adding bitterly, "If I can't exchange the hundreds, I'll paste them on my bedroom window to keep the draft out and look at them as I die."

Many economists see currency reform of the kind ordered by President Mikhail S. Gorbachev Tuesday night as a prerequisite for freeing prices and creating a market economy.

Without it, billions of excess rubles turned out by Soviet government printing presses over the last few years threaten to turn free prices into destructive hyperinflation. Criminals could use their millions to buy up a big percentage of state enterprises, compromising the conversion of state enterprises into private ones.

The decision to cancel, and eventually replace, only the two biggest-denomination notes was aimed at the shadow economy. Black marketeers tend to use 50s and 100s, government officials say, and such notes account for about a third of all the rubles in circulation. Any money that cannot be shown to have been earned honestly will be withdrawn from circulation, theoretically leaving the ruble stronger.

But some economists were skeptical about the impact. Boris Pinsker, who writes on economic issues, criticized the plan in the newspaper Vechernaya Moskva as likely to remove an insignificant amount of currency from the market.

Moreover, Mr. Pinsker said, the biggest impact will be on "not-so-rich people, such as old women in the villages." He said black marketeers responded to the rumors of currency reform over the last two months by ridding themselves of large-denomination notes and putting their money in gold, automobiles or other goods.

Despite the rumors, the suddenness of Tuesday night's decree created chaos across the country yesterday.

Post offices and savings banks ran out of money. Commissions assigned to decide what constitutes "honest" savings were just being formed.

Representatives of the cooperative movement said they feared that profits from their fledgling private businesses would be confiscated. Ordinary people were baffled by the complicated language of the Gorbachev decree, read on radio and television without a translation into plain Russian.

Personal predicaments were many. Maria V. Elkonina, a Moscow artist, had just withdrawn 3,000 rubles in hundreds to pay for arrangements for an exhibit.

Technically, she said, she is a pensioner, so she has to prove that she earned 2,800 of the 3,000 rubles. By the time a commission is set up to rule on her savings, it will be too late for the exhibit, set for March, she said.

"It's humiliating," said Alexander N. Krylov, 50, a factory technician who earns 200 rubles a month. He can change the amount of one month's pay with no documentation but will have to prove he earned the other 500 rubles he has in large bills.

But Mr. Krylov said he thought some kind of ruble reform was necessary. "We have a big Mafia, and they carry around suitcases of 100s," he said.

Not any more. Down the street at Moscow's Central Market, the fruit and flower vendors are among the richest of Soviet citizens, earning in many cases several thousand rubles a month. But several acknowledged that they had been tipped off that the reform was coming.

"I haven't taken anything bigger than 25 rubles since December," said Volodya, from Azerbaijan, hawking tomatoes for 20 rubles a kilogram.

Some of the market's wheeler-dealers, he said, were buying 50s and 100s for half their face value in negotiable smaller denominations.

What will they do with the bills they buy? he was asked.

"They can get rid of them. They have connections on the very highest level," he said with a smile.